StreetMeasure app
StreetMeasure is an app to measure distances and heights. It is based on the non-free Google ARCode and thus was separated from the otherwise free/libre open-source StreetComplete a.o. in order to have the latter available at F-Droid.org – and also to make it your choice whether you're willing to accept a non-free component while remaining able to use StreetComplete no matter how you decide.
StreetMeasure was made for usage with StreetComplete and other OpenStreetMap editors. But you can use it for other things, too.
In order to use this app, you will need to have the proprietary Google Play Services for AR app installed on your device as well.